An organic electroluminescence device (also referred to as “organic EL device”) generally comprises an anode, a cathode, and an organic thin film layer comprising one or more layers between the anode and the cathode. When a voltage is applied between the electrodes, electrons are injected from the cathode and holes are injected from the anode into a light emitting region. The injected electrons recombine with the injected holes in the light emitting region to form excited states. When the excited state returns to the ground state, the energy is released as light. Therefore, it is important for increasing the efficiency of an organic EL device to develop a compound which transports electrons or holes into a light emitting region efficiently and facilitates the recombination of electrons and holes.
Patent Literature 1 describes an amine compound wherein 9,9′-spirobifluorene, 9,9-dimethylfluorene, and phenanthrene are directly bonded to the same nitrogen atom. Patent Literature 1 describes that this amine compound is suitable as a hole transporting material, but, the performance of an organic EL device comprising this amine compound is not described.
Patent Literature 2 describes an amine compound wherein 9,9′-spirobifluorene, triphenylene having three phenyl substituents, and an arene selected from benzene, naphthalene, 9,9-dimethylfluorene, phenanthrene, etc. are directly bonded to the same nitrogen atom. Patent Literature 2 describes that this amine compound can be used in a light emitting layer or a hole transporting layer, but, the performance of an organic EL device comprising this amine compound is not described.
Patent Literature 3 describes an amine compound wherein a substituted or unsubstituted triphenylene, 9,9-dimethylfluorene, and biphenyl or terphenyl are bonded to the same nitrogen atom. An organic EL device actually produced in the working examples includes the amine compound in a hole transporting layer.
Patent Literature 4 describes an amine compound wherein biphenyl, 9,9-diphenylfluorene, and a triphenylene having a phenyl substituent are bonded to the same nitrogen atom. Patent Literature 4 describes that this amine compound is used in a hole transporting layer, etc., but, the performance of an organic EL device comprising this amine compound is not described.
The amine compounds described in Patent Literatures 1 to 4 are still required to be improved in their performances as organic EL devices, particularly in the driving voltage and the lifetime.